Question

4. Write the number of periods the modern periodic table has. How do the valency and metallic character of elements vary on moving from left to right in a period? How do the valency and atomic size of elements vary down a group?

Answer 1

7 period in periodic table

Explanation:

on moving left to right valency increases from 1 to 4 then decreases from 4 to 1 and metallic character decrease while going left to right of periodic table . down a group valency remain same and atomic size increases